The invention relates to a device for holding together and releasing conical joints, in particular on laboratory apparatus, consisting of a conical pin and a conical sleeve according to the preamble of claim 1. Devices of this kind act on the one hand as fixing elements, for example for connecting a glass plunger with a conical ground joint in a positively locking manner to laboratory apparatus having a complementary conical ground joint.
Since conical ground joints are often difficult to separate again due to changes in temperature, deposits etc, the nut generally also serves to ease the release of the joint by being rotated in the opposite direction in order to push out one of the two connected parts. A generically comparable device is already known, in which the nut is screwed on to an outer thread, the thread abutting directly against the conical pin and having a core diameter of the same size or greater than the greatest external diameter of the cone. The clamping device consists of segment-like aprons extending downwards over a circumferential area of 180.degree. on the nut, an inwardly oriented projection being disposed on the ends of the said aprons for engaging behind the swelling on the conical sleeve. The conical sleeve with the swelling is inserted laterally into the clamping device of the nut and then pushed, together with the nut, over the conical pin and screwed on.
A slightly different solution is proposed in FR-A-2 589 221, wherein the outer thread is disposed on the conical sleeve and not on the conical pin. The nut is in this case formed as a union nut and, when connected, bears against a collar on the conical pin.
A disadvantage of the known devices is that the conical sleeve or the glass plunger abutting it can only be removed when the nut is completely unscrewed from the outer thread. This is especially time-consuming in cases where the conical ground joint is released automatically and where it is not necessary to press by means of the nut. Furthermore, during handling, the nut may drop out and be lost. A further disadvantage of known devices is that the greatest outer diameter of the cone must be smaller than the outer thread, in order that the nut can be screwed on. In certain cases, however, it would be desirable to be able to use relatively large cone diameters without the necessity for the thread on the conical pin to be correspondingly larger.